Ghost calls correlated to signal on TX line


Celeron 2.0GHz
Slackware 11.0
X100P compatible card interfacing the PSTN in UK (Virgin Media as telco).

I am having this problem with ghost calls coming on the line (several times a day, sometimes several times in 10 minutes, no regular pattern). If I plug in a normal phone on the same line - it doesn’t ring during the ghost calls.

I have managed to narrow it down to the following:

  1. With ztmonitor running - I can see the TX line (which normally has nothing on it when on-hook) increases and decreases the level in the rithm/pattern of the rings. When a real call come in - it is the RX line which does this. It looks like somehow - when one of my neighbours (probably) has an incoming call - my TX line gets the ringing signal as well.

I have two questions:

  1. Is there any way to convince zaptel/Asterisk to ignore the ‘fake’ calls coming on the TX line and to only answer the ones on the RX line? Maybe by hacking at the code somwhere? I was thinking of calling the telco - but considering the ‘normal’ phones don’t ring during the ghost calls - it might take some convincing that there is a problem with their lines.

  2. The RX line shows full/top/100% signal permanently when on-hook (with some slight variation). Is that normal - is it how it works? Also, a sub-question :smile: - do the levels in ztmonitor reflect the actual voltage on the line, or some other characteristic of the line?

Many thanks for any suggestions